Large, high-power, single-pole electrical connectors are used in a variety of industrial settings. One such setting is the oil and gas exploration and production industry. This industry can be divided into two major segments: offshore operations and land-based operations. This distinction is important for a number of reasons, including the type of electrical systems used.
Offshore oil and gas operations typically use semi-permanent electrical systems. These systems may be more resistant to the sometimes extreme environmental demands and may provide increased reliability. In these systems, there often are more hard-wired connections (i.e., as compared to land-based operations), and fewer single-pole electrical connectors of the general type discussed below.
Land-based oil and gas operations, on the other hand, typically use more portable systems. In many instances, most of the equipment, perhaps all of it, is transported to the site using a commercial truck. This means the equipment must not exceed the size limits of such trucks. In practical terms, this frequently means that single pieces of equipment cannot be more than eight to nine feet wide or tall.
These constraints have significant impact on the design of electrical distribution systems for land-based operations. Land-based operations have become increasingly complex, with many land-based operations now involving long horizontal drilling runs or other complex, steered drilling operations. With the increase in complexity comes an increase in the equipment and power demands. For example, in operations that involve long drilling runs, more and more powerful equipment may be needed.
These demands mean more electrical loads. More electrical loads means more electrical supply and distribution lines. And more lines means more connections on the distribution panel. In a typical land-based drilling operation, a prefabricated “box” is used for the electrical supply and distribution hub. This box has one or more sides that are designed for use as a distribution panel. On this panel will be mounted many electrical receptacles, which are designed to accept cable-end plugs. The cables run from the distribution panel to the electrical equipment. At the distribution panel, there are typically a large number of panel-mounted receptacles (of either male or female design). When the system is fully made up, there are many cables running to the panel, with each cable having a plug that is connected to a matching receptacle.
As the number of size of the electrical loads on land-based rigs has increased, the number of panel-mounted receptacles has increased. It is now common to find distribution panels completely filled with panel-mounted receptacles. And even that is sometimes not enough.
The same situation may occur in other industrial settings. Indeed, there may be many situations where there is a need or desire to reduce the overall size of a distribution panel or to fit more receptacles on such a panel. The present invention may be of benefit in all these situations.
There are only a few ways to get more receptacles on a distribution panel. First, the spacing between receptacles could be reduced. This is already done on many installations. Moreover, certain panel-mount receptacles provide designs that are more conducive to such close spacing, and thus allow for more receptacles on a given size panel. This solution is limited, however, because there must be room to install the receptacles and make up the connections while retaining enough surface material of the panel to ensure the panel retains sufficient strength to support all the connectors and cables running to and from the panel.
A second solution is to make the distribution panels larger. For land-based oil and gas operations, this solution is limited by the size of the standard commercial truck and the desire to prefabricate the electrical box. Given these constraints, there is limited room for change in the size of the panel.
A third solution is to make the connectors smaller. If the panel-mounted receptacles and cable-end plugs are smaller, more of them will fit in a given space. There is, however, a drawback to this “solution.” Smaller connectors typically have lower power ratings. If connectors with lower power ratings are used, it is quite possible, and probably quite likely, that more connectors will be needed to supply the loads. This result tends to defeat the purpose of using smaller connectors. This may be one reason that most land-based drilling rigs use only high-power connectors. Going to smaller connectors might only make the situation worse, by requiring use of even more connectors.
There is a need for a downsized high-power connector. The need is not for merely a smaller connector with a lower power rating, but for a physically smaller connector that provides the same, or nearly the same, power ratings as the large connectors in wide use today. This need has existed for a long time, but it has become more acute as the competition increases for space on fixed-size electrical distribution panels.
High-power, single-pole connectors are typically made of several parts, which are assembled in a specific process. The core conductor, for example, is typically positioned within a rigid insulating sleeve, which is then placed inside a strong, metal shell. The sequence of these steps is not critical in most instances, as the insulating sleeve may be installed in the outer shell first, and the core conductor then installed inside the insulating sleeve. But regardless of the assembly sequent, it is critical that the axial positioning of the parts be maintained in use. To achieve that result, some type of retaining structure is used between the various parts. The core conductor, for example, is typically fixed in position relative to the rigid insulating sleeve with slip rings.
This design is described in more detail below (see FIGS. 4-5), but suffice it to say that space is required inside the connector for the retaining hardware (e.g., slip rings), including some space for the installation and possible removal of such hardware. This spacing is one factor in fixing the overall physical size of a particular connector. The core conductor is sized to provide a certain power rating, with larger conductors being rated for more power. The core conductor is typically of a size roughly comparable to that of the core of the electrical supply and distribution cables. The rigid insulation is sized based on the needed amount of insulation given the power rating of the connector. An additional amount of space is needed if the connector is to be sealed from water intrusion. Generally an O-ring is installed between the contact and the insulator and a second O-ring is installed between the insulator and the outer shell. The rigid insulator must also be sized to allow radial spacing to allow for the outer diameter of the contact plus the retaining ring and must also allow radial spacing for the O-rings if sealing is required.
None of these variables appears subject to alteration, and in fact, prior art connectors of this type are subject to all the limitations described above. The present invention, however, marks a significant change. The core conductor is no longer retained by slip rings or other similar hardware. Instead, an insulating axial positioner is used, as described below. This change in the design of the axial positioner allows the elimination of any radial spacing previously required for either a retaining ring or sealing O-rings. The entire radial distance between the outer diameter of the contact and the inside of the shell can be used for insulation thickness. Through use of this positioner and related changes to other components, the present invention is able to provide a downsized high-power, single-pole electrical connector.
Connectors of this type are housed in shells of standard sizes. The largest connectors use a size 24 shell. Connectors of this type may be used with cable sizes 646 mcm and 777 mcm. When used with these cables, a connector of this type may have current ratings as high as about 1000 A and 1100 A, respectively. A smaller connector might use a size 20 shell, but only be able to handle cable size up to 444 mcm. That configuration would typically provide a maximum current rating of about 800 A. This is a full 20% or more below the current ratings for a larger, size 24 shell connector.
The present invention provides a connector using a size 20 shell that can accommodate up to size 646 mcm cable. That means a size 20 shell connector embodying the present invention may have current rating of about 1000 A. The size 20 shell is about 20% smaller than the size 24 shell, resulting is a significant space savings. More of these downsized connectors may be installed on a given distribution panel without a loss of power capacity per connector. In fact, the present invention will work with even size 777 mcm cable. At present, however, the standard fittings used with cable of this size (e.g., the cable clamps) are larger than a size 20 housing, and the fittings become size limiting. By reducing the size of those components, it would be possible to use even size 777 mcm cable in a size 20 shell with the present invention.
These specific examples are merely illustrations of the benefits of the present invention. As the description provided below will make clear, the invention may be used to reduce the overall size of any high-power, single-pole electrical connector. This size reduction has other benefits, as well, because it is a smaller, lighter overall product. It takes up less space in storage, costs less to ship, and is easier to handle due to the reduced weight. All of these benefits are achieved without any loss of safety margin.
In a preferred embodiment, the present invention includes a core conductor, having a contact end, a cable end, and a retaining groove positioned near a midpoint between the contact end and the cable end; a rigid cable end insulator positioned radially outward of the core conductor and extending from the cable end to a point near the retaining groove; a rigid contact end insulator positioned radially outward of the core conductor and extending from the contact end to a point near the retaining groove; an insulating axial positioner located between the rigid cable end insulator and the rigid contact end insulator, the insulating axial positioner having a radially inner side and a radially outer side, the radially inner side inserted in the retaining groove of the core conductor; and, a shell positioned radially outward of the rigid cable end insulator, the rigid contact end insulator, and the insulating axial positioner.
An alternative embodiment of the present invention includes the following steps: inserting an insulating axial positioner into a retaining groove in a core conductor; inserting a first rigid insulator into a shell; inserting the core conductor into the first rigid insulator, such that the insulating axial positioner is in contact with the first rigid insulator; inserting a second rigid insulator into the shell; and, securing a barrel to the shell, such that the first and second rigid insulators compress the insulating axial positioner.